ALMA spectra of V1309 Sco (black) and their simulations (red). The observed spectrum was extracted for the central beam of the molecular region and is displayed in the Rayleigh–Jeans brightness temperature scale. In the CASSIS simulation, we adopted excitation temperatures of 36 K for CO and of 80 K for most other species (see text). SO, SO₂, and AlO were modelled with two velocity components.